1. Field of the Invention
This invention relates generally to the field of Optics and more specifically to dual stereo-microscopes for use in performing micro-surgery.
2. Description of the Prior Art
The performance of surgery under a microscope has become increasingly popular in recent years, particularly in areas of the body such as the eye and inner ear where precision is imperative. The instrumentation for performing such work has barely kept pace with the increasing needs in the field. Of particular importance is proper illumination at the right level of intensity and at the right location when required by the surgeon.
All presently available operating microscopes were initially constructed to provide a good view of the operative field for one surgeon. As the necessity for the assistant to view the operative field was recognized, either light was taken from the surgeon's view by means of a beam splitter as in the Zeiss operating microscope, or a separate optical system was attached to the body of the microscope as in the Weck microscope. The assistant viewing system of the Zeiss microscope has the obvious disadvantage of decreased illumination for the surgeon and assistant and loss of stereopsis for the assistant. A new attempt by Zeiss to give the assistant a stereoscopic view still has the disadvantage of using beam splitters which decrease the light intensity and the Zeiss arrangement provides much less stereopsis for the assistant than for the surgeon. An older modification by Zeiss using a pentagonal prism and two light sources allows equal stereopsis and light intensity for the surgeon and assistant but requires that the two viewers sit 180.degree. apart, a situation unfeasible for eye surgery.
The disadvantage of the Weck assistant microscope is that the assistant sees the procedure from an entirely different angle and in the case of vitrectomy and other intraocular procedures the assistant has no view of intraocular structures.
In most operating microscopes currently available, the illumination system for the area of surgery is internal of the microscope. Examples of such systems are shown in the U.S. patent to Littmann, No. 3,186,300 and the U.S. patent to Riedel No. 3,170,983. Each of these patents shows a dual, stereomicroscope arrangement with dual internal light sources and prisms for diverting and directing the light beams from the light sources to the area of surgery and back to the eyes of the observer. Such arrangements produce internal relfections from the light source which interfere with the observed light available to the surgeon. Such systems also generally use a prism as a beam-splitter for assistant viewing and photographic capabilities, thereby reducing the available incident light to the surgeon. The illumination rays also occupy a large portion of the available space within the instrument, thereby reducing the space available for transmission of viewing light to the observers.